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1%イントロ・ヒストリー:USB Power for Remington MB4040.

2020年11月12日 - Make A. Mendによって編集

承認済みの編集 : Make A. Mend

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Introduction

== '''WHY I DID THIS''' ==

* Great shaver, but I got tired of buying a new one every time the rechargeable battery failed. Shaving only half my face per charge wasn’t going to work. ;-)

* I don’t need the rechargeable capability, so modified the electronics to work on power from a USB connector.

== '''NOTE''' ==

* Review this entire guide before considering trying something similar yourself.

* This solution will require the shaver to be plugged in while shaving (and unplugged afterwards).

* The shaver will not be rechargeable afterwards.

* The on/off switch and LED will no longer function.

* The PCB version of my shaver was Rev 2.1.

== '''SKILLS''' ==

* Unsoldering devices from a PCB board.

* Soldering wires together and to a PCB board.

* Using heat-shrink tubing or electrical tape.

* Measuring DC voltages.

== '''WARNING''' ==

* Removing a battery and powering directly from the wall removes electrical isolation and thus is more dangerous.
* Do NOT use in wet environments such as a wet floor, bathtub, shower enclosure, etc.
* Do NOT use if your are wet or shaving with foam.

* I make no commitments that this guide is safe. This is strictly a guide of what I did and works fine for me.

== '''REPAIR STRATEGY''' ==

The following will be discussed in further detail during the guide:

'''SHAVER MODIFICATIONS'''

* Convert shaver’s internal power circuit from AC to DC (so it will work from USB wall adapter).

* Remove battery and unnecessary electronics on PCB.

* Use existing parts in place for mechanical and electrical continuity.

'''CABLE MODIFICATIONS'''

* Cut off old power adapter and keep the cable (with the shaver connector).

* Cut off non-USB-A end of a USB-A cable and keep the USB-A end.

* Connect the old power cable (with shaver connector) to the USB-A cable.

== '''REPAIR THEORY''' ==

* To figure out power levels, I measured the battery voltage after charging. It was 4.0 VDC. I also measured the current draw which was 100mA, also at about 4 V.

* Since the device came with an AC charger, I planned to replace it with a DC USB-A adapter which provides 5VDC.

* I empirically tested that with one forward diode drop I could get the the motor running at 5he same 4 VDC and 100mA current

* To maintain mechanical and electrical connection to the shaver through the old power cable, I needed to leave the PCB fixed in place, but removed most of the rectification diodes except one. That extra diode provides the voltage drop to get the motor voltage down to around 4 volts. I also removed the capacitor, battery, and battery heat sensor (see photos later).